The purpose is to investigate the auditory capacities of severely hearing-impaired persons to discriminate various qualities of complex auditory stimuli, especially those qualities that are important in speech perception. The method is to compare abnormal and normal audition using tests of auditory discrimination and identification of synthetic sound stimuli having known acoustical characteristics. The comparisons are made so as to develop new psychoacoustic information on the speech-perception problems of persons with sensorineural hearing loss. Both young and elderly listeners are studied. Discrimination and identification measures are carried out for known timbre differences among vowel sounds, simulated consonant sounds, and sound spectral patterns which vary in time, such as format transitions.